Synthesis, bioactivity, and the anion-binding property of 2-sulfydryl-1,3,4-thiodiazole derivatives

Article abstract of DOI:10.1002/hc.21239

Two new compounds (1 and 2) containing 2-sulfydryl-1,3,4-thiodiazole have been synthesized and optimized. They both showed wide antibacterial activity for colon bacillus, Staphylococcus aureus, S. albus, dysentery bacillus and inferior activity for Bacillus subtilis. In addition, their binding properties were evaluated for biologically important anions (F^-, Cl^-, Br^-, I^-, AcO^-, and H₂PO₄ ^-) by theoretical investigation, UV-vis, fluorescence, and ¹H NMR titration experiments, and they displayed strong binding ability for H2PO4 - without the interference of other anions tested. Especially the binding ability of compound 2 containing anthracene with H₂PO₄^- was 1000 times stronger than that of compound 1 containing nitrobenzene. Two compounds based on 2-sulfydryl-1,3,4-thiodiazole have both properties of anion recognition and antibacterial activity.

Full text of DOI:10.1002/hc.21239

Heteroatom Chemistry
Volume 26, Number 2, 2015
S
ynthesis, Bioactivity, and the Anion-Binding
Property of 2-Sulfydryl-1,3,4-thiodiazole
Derivatives
1
2
3
3
Xuefang Shang, Wanli Li, Xiaofang Wei, Huanle Zhang,
3
3
4
Zhiyuan Fu, Jinlian Zhang, and Xiufang Xu
1
Department of Chemistry, Xinxiang Medical University, Xinxiang, Henan 453003, People’s
Republic of China
2Department of Immunity, Xinxiang Medical University, Xinxiang, Henan 453003, People’s
Republic of China
3School of Pharmacy, Xinxiang Medical University, Xinxiang, Henan 453003, People’s Republic of
China
4Department of Chemistry, Nankai University, Tianjin 300071, People’s Republic of China
Received 12 June 2014; revised 27 July 2014; accepted 2 September 2014
2
6:142–149, 2015; View this article online at wiley-
ABSTRACT: Two new compounds (1 and 2) con-
taining 2-sulfydryl-1,3,4-thiodiazole have been syn-
thesized and optimized. They both showed wide
antibacterial activity for colon bacillus, Staphylococ-
cus aureus, S. albus, dysentery bacillus and inferior
activity for Bacillus subtilis. In addition, their bind-
ing properties were evaluated for biologically impor-
onlinelibrary.com. DOI 10.1002/hc.21239
INTRODUCTION
–
–
–
–
–
–
tant anions (F , Cl , Br , I , AcO , and H2PO4 ) by
Selective recognition and sensing of specific anions
have been becoming an area of research focus in the
field of supramolecular chemistry because anions
play very important roles in many chemical, biolog-
ical, and environmental systems [1–4]. For example,
the amount of fluoride intake within the human
body is closely relevant to dental care, osteoporosis,
and fluorosis [5]. Carboxylate ions are vital compo-
nents of many human metabolic processes [6]. The
phosphate anion and its analogs are significantly
involved in signal transduction and energy storage
in a biological system [7]. So far, the focus has
been mainly on the design of a receptor that has
the ability to recognize and bind the biologically
important anions. The binding units in receptors
are important and often composed of amide [8],
urea [9], hydroxyl [10, 11], and pyrrole [12] owing
to their capacity to perform as hydrogen donors.
1
theoretical investigation, UV–vis, fluorescence, and H
NMR titration experiments, and they displayed strong
binding ability for H2PO4– without the interference
of other anions tested. Especially the binding ability
–
of compound 2 containing anthracene with H2PO4
was 1000 times stronger than that of compound
1
containing nitrobenzene. Two compounds based
on 2-sulfydryl-1,3,4-thiodiazole have both proper-
ties of anion recognition and antibacterial activity.
ꢀC
2014 Wiley Periodicals, Inc. Heteroatom Chem.
Correspondence to: Xuefang Shang; e-mail: xuefangshang@
26.com.
1
Contract grant sponsor: National Natural Science Foundation
of China.
Contract grant number: 81301269.
ꢀ
2014 Wiley Periodicals, Inc.
C
142

Synthesis, Bioactivity, and the Anion-Binding Property of 2-Sulfydryl-1,3,4-thiodiazole 143
SCHEME 1 General synthetic route to the target compound 1 and 2.
However, sulfydryl (–SH) serving as a binding site
to recognize an anion has almost not been reported.
The synthesis and functionalization of thiodia-
zole derivatives [13] have long been of great interest
to the chemistry community because of the vast po-
tentials and demands for thiodiazole derivatives in
diverse fields, such as disinfection, weedicide, and
sterilization. Thiodiazole derivatives were reported
to exhibit a variety of biological activities. However,
almost no literature is available on anion-binding
ability based on 2-sulfydryl-thiodiazole derivatives
currently.
RESULTS AND DISCUSSION
UV–Vis Spectral Titration
To research on the anion-binding ability of two com-
pounds (1 and 2), UV–vis titrations were carried out
−5
−1
−
in DMSO at a concentration of 4.0 × 10 mol·L
by adding tetrabutylammonium salts of H PO
4
2
−
(Fig. 1). The presence of H PO resulted in appear-
2
4
ance of the absorbance bands at 322 and 480 nm due
to gradual decreasing and increasing in the intensity,
respectively. In addition, two isosbestic points ap-
peared at 360 and 305 nm, indicating the formation
of a stable host–guest complex. The redshift phe-
nomenon occurred during the interaction process of
host–guest. The significant color changes from col-
orless to yellow indicated the intramolecular charge
transfer between the anion binding with the –SH
On the basis of the above considerations, we re-
port the synthesis, antibacterial activity, and recog-
nition properties of 2-sulfydryl-1,3,4-thiodiazole
derivatives in this paper (Scheme 1). The experi-
mental results showed that two compounds could
−
effectively recognize and sense H2PO4 in dimethyl
moiety and the electron-deficient –NO moiety [14].
2
sulfoxide (DMSO). To our delight, two compounds
also showed wide antibacterial activity.
Especially, the changes in the UV–vis spectra were
attributed to the interactions between the –SH sites
−
5
−1
−
2 4
PO
((0–160) × 10−5
FIGURE 1 UV–vis spectral changes of two compounds (4.0 × 10 mol·L ) upon the addition of H
−
1
mol·L ): (a) 1 nd (b) 2. Arrows indicate the direction of increasing anion concentration.
Heteroatom Chemistry DOI 10.1002/hc

144 Shang et al.
−
5
−1
−
4
FIGURE 2 Changes in the emission spectra of compounds (4.0 × 10 mol·L ) in the absence and presence of H
2
PO
−
5
−1
(
(0–80) ×10 mol·L ): (a) compound 1, λex = 284 nm; (b) compound 2, λex = 355 nm. Arrows indicate the direction of
−
increasing H
2
PO
4
concentration.
−
of the thiadiazole subunits and H2PO4 via the H
bond. In addition, as the intensity of the polarization
increased by the –NO2 substituent, the electron den-
sity of the –SH moiety was transferred to the nitro
moiety, resulting in the possibility of realizing visual
inspection. It is well known that upon the addition
of the protic solvents such as water or methanol will
competitively result in hydrogen bonding with the
binding site of a receptor for anions. After the inter-
gated. Just as Fig. 2 showed, compound 1 exhibited
an emission peak centered at 352 nm. Upon the ad-
dition of H2PO4 into the solution of compound 1,
−
the fluorescence emission was decreased obviously.
To account for such fluorescence quenching, the
photoinduced electronic transfer (PET) mechanism
was exploited. For compound 1, the excited state
of the fluorophore was not, or only to a minor
extent, quenched by the electron transfer from the
receptor to the fluorophore prior to the sensor–
anion interactions. However, upon the interaction
with anions, the reduction potential of compound
1 was increased and the electron transfer from the
electron-rich –HS moiety bonded with the anion to
the electron-deficient –NO2 moiety became more
feasible [16]. Therefore, the fluorescence intensity
of compound 1 was quenched upon the addition of
anions.
−
action between compound 1 and H2PO4 , a small
quantity of a protic solvent (such as H2O or MeOH)
was added for the complexation. Then, the yellow so-
−
lution (1- H2PO4 ) reverted to colorless, which was
the color of the solution of compound 1. The above
observation showed that the interaction of the host–
guest complex was reversible. The presence of the ac-
etate ion showed similar changes in UV–vis spectra.
−
−
−
−
However, the additions of F , Cl , Br , and I virtu-
ally led to very weak spectral response to compound
For compound 2, the fluorescence emission cen-
tered at 405 nm was gradually strengthened and
shifted to the long wavelength centered at 425 nm
1, which indicated that the interactions of the host–
guest complex were very weak and could be ignored.
As for compound 2, the intensity of the absorp-
tion peak at 450 nm decreased and a new absorption
−
(ꢀλ = 20 nm) upon the addition of H2PO4 . Such
a fluorescent enhancement could be rationalized
on the basis of two possible signaling transduction
−
peak at 500 nm appeared when H2PO4 was added.
Clearly, redshift phenomenon occurred in host-guest
interaction. At the same time, one clear isosbestic
point appeared at 497 nm, which indicated that com-
−
pound 2 interacted with H2PO4 by hydrogen bond-
ing, and the stable complex was formed [15]. The
−
−
addition of AcO and F induced similar spectral
changes in compound 2. However, the additions of
−
−
−
Cl , Br , and I virtually led to very weak spectral re-
sponse to compound 2, which indicated that the in-
teractions of the host–guest complex were very weak
and could be ignored.
Fluorescence Response
FIGURE 3 Fluorescence changes of compound 2 (4.0 ×
−
5
−1
−4
The photophysical response of two compounds
toward addition of anions tested was also investi-
10
mol·L ) upon the addition of anions (8.0 × 10
−
1
mol·L ).
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Bioactivity, and the Anion-Binding Property of 2-Sulfydryl-1,3,4-thiodiazole 145
TABLE 1 Binding Constants of Two Compounds with Vari-
ous Anions Based on UV–Vis Data
Aniona
K
(1)
s
s
K (2)
–
3
3
6
5
4
H
2
PO
4
(1.34 ± 0.08) × 10
(4.49 ± 0.92) × 10
2
2
R = 0.999
R = 0.992
−
AcO
(1.09 ± 0.15) × 10
(1.14 ± 0.06) × 10
2
2
R = 0.983
R = 0.984
−
F
32.2
(1.97 ± 0.41) × 10
2
2
R = 0.998
R = 0.983
−
−
−
b
Cl , Br , or I
ND
ND
aAll anions were added in the form of tetra-n-butylammonium
salts.
b
The spectral changed little and could not be determined
FIGURE 4 A Job plot for complexation of compound 2 with
−
−
−
−
AcO or F (Fig. 3). On the other hand, no signifi-
cant spectral changes were observed upon the titra-
H
2
PO
4
determined by UV–vis in DMSO. [2] + [ H
2
PO
4
] =
−
5
−1
4
.0 × 10 mol·L
.
−
−
−
tion of 2 with Cl , Br , and I , signifying compound
showed insignificant binding affinity toward these
2
anions.
mechanisms: (1) inhibition of PET [17, 18] and (2)
binding-induced rigidity of the host molecule [19,
2
0]. Before complexation with anions, there was PET
Binding Constant
from the thiodiazole to the anthracene unit, result-
ing in a weak emission. Upon binding with anions,
the above-mentioned PET would be inhibited and as
a result a fluorescent enhancement was observed. In
addition, it has been well known that complexation-
induced rigidity of a fluorescent receptor has been
reported to result in a large increase in the emission
intensity because of inhibiting vibrational and rota-
tional relaxation modes of nonradiative decay. Weak
spectral changes were observed upon the addition of
The job–plot curve (Fig. 4) indicated that the spec-
tral change could be ascribed to the formation of 1:1
host–guest complexation. Nonlinear fitting curves
are shown in Fig. 5, and the corresponding bind-
ing constants are listed in Table 1 using the method
of least-squares calculation according to the UV–vis
data [21–23]. The binding ability trend of two com-
−
pounds to anions followed the order of H2PO4
>
−
−
−
−
−
AcO > F >> Cl ꢀ Br ꢀ I . Two compounds both
FIGURE 5 Nonlinear fitting curves between two compounds and anions.
Heteroatom Chemistry DOI 10.1002/hc

146 Shang et al.
−
showed the strongest binding ability for H2PO4 ,
which involved multiple hydrogen bonds. It was
apparent that multiple hydrogen-bond interactions
were important in high-affinity anion-binding sites.
For the same anion, the binding ability of compound
2
containing anthracene was stronger than that of
compound 1 containing nitrobenzene. Especially for
−
H2PO4 , the binding constant of compound 2 was
1000 times more than that of compound 1. The num-
ber of binding sites for 1 and 2 was two and one, re-
spectively. Although the number of the binding sites
of compound 2 was less than compound 1, the dis-
tance of two hydrogen atoms in binding sites (–HS)
˚
of compound 1 was far away, 16.731 A, according
to theoretical investigation (in the following text).
So, the anion-binding ability of 2 was strong and the
binding constants of 2 for all anions were more than
those of 1.
FIGURE 7 Portion of 1H NMR spectra of compound 2
−
1
(
0.02 mol·L ) in DMSO-d
6
in the presence of increasing
−
amount of H
2
PO
4
: (a) free 1, (b) 1 + 0.5 equiv, (c) 1 + 1.0
equiv, (d) 1 + 2 equiv, and (e) 1 + 5 equiv of [(n-Bu)
4 2 4
N]H PO .
Interference Experiment
1H NMR Titration
−
The binding ability of two compounds with H2PO4
was the strongest among the anions tested according
to the binding constants. The above results derived
on the condition that only one anion existed. The
interference experiment was conducted to explore
To further study the binding character of receptor–
guest interactions, H NMR titrations were carried
1
out in DMSO-d . For compound 2, the proton signal
6
at 14.65 ppm could have resulted from the –SH of the
−
−
whether the binding ability of H2PO4 was influ-
thiodiazole moiety in the absence of H PO (Fig. 7).
2
4
−
enced by other anions (Fig. 6). According to UV–vis
experimental data, the intensity of spectral response
to compound 2 was different when various anions
After 0.5 equiv of H PO was added, the signal of
2 4
–SH was broadened and weakened. What’s more,
the proton of Schiff base (H4) shifted to the upfield
direction and the protons of anthracene (H1, H2,
and H3) were almost showing no changes. After 1
−
−
−
−5
−1
(
H2PO4 , AcO , and F ; 4.0 × 10 mol·L ) were
added separately. As shown in Fig. 6, the spectral re-
−
sponse of 2 upon the addition of mixed anions was
equiv of H PO was added, the signal of the –SH
2
4
−
almost as the same as the addition of only H2PO4 ,
was disappeared thoroughly, which indicated that
the interacted site of host–guest was the –SH moiety
−
which indicated that the binding ability of H2PO4
with compound 2 was not interfered by the existence
of other anions.
and the hydrogen-bonding complex was formed at
−
this stage between compound 2 and H PO
2
4
.
Antibacterial Activity
Antibacterial activity of the synthesized 5-sulaydryl-
thiodiazole derivatives was tested by the agar well-
dilution method (Table 2). The reference solution did
TABLE 2 In Vitro Antibacterial Activity of Two Compounds
(
n = 8)
Compound
Bacterium
1
2
Colon bacillus
21.96 ± 4.01**
18.38 ± 4.65**
19.55 ± 4.77**
15.61 ± 3.39**
4.86 ± 1.73
19.36 ± 5.84**
22.62 ± 5.41**
23.51 ± 6.89**
20.13 ± 5.84**
4.23 ± 2.72
Staphylococcus aureus
Staphylococcus albus
Dysentery bacillus
Bacillus subtilis
FIGURE
6
UV–vis spectral changes in compound
2
−
5
−1
(
4.0 × 10 ) m. ol·L ) upon the addition of anions (4.0 ×
−
5
−1
1
0
mol·L
Compared with B. subtilis: **P<0.01
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Bioactivity, and the Anion-Binding Property of 2-Sulfydryl-1,3,4-thiodiazole 147
FIGURE 8 Optimized structures of two compounds.
not show any antibacterial activity for the bacteria
tested. From Table 2, two compounds showed wide
antibacterial activity, especially for Colon bacillus,
Staphylococcus aureus, S. albus, and Dysentery bacil-
lus. However, they both showed very weak sensitivity
against Bacillus subtilis which could be ignored. The
above results could provide reference data for the
further study of antibacterial activity of 2- sulfydryl-
was weaker than those of triangle and tetrahedron
−
−
ions (AcO and H2PO4 ). According to geometries of
compound 1 and 2, multiple hydrogen bonds were
important in anion-binding ability.
In addition, selected frontier orbitals for two
compounds are shown in Fig. 9. We introduced
molecular frontier orbital to explain UV–vis absorp-
tion spectra in the host–guest interacted process by
electron transition of frontier orbital. The highest oc-
cupied orbital (HOMO) density in compound 1 was
mainly localized on the whole molecular, whereas
the lowest unoccupied orbital (LUMO) density was
localized on the benzene cycle moiety, which demon-
strated that it was the electron transition of LUMO to
arouse the redshift phenomenon in UV–vis spectra
of host–guest. The similar result was also observed
in compound 2.
1,3,4-thiodiazole derivatives.
Theoretical Investigation
The geometries of two compounds (1 and 2) were op-
timized (Fig. 8) using the Hartree–Fock method with
basis sets 3-21G. The calculation was performed
with Gaussian03 program [24]. From Fig. 8, the
distance of two hydrogen atoms in –SH of com-
˚
Compound 1 may form cis or trans isomers in
both Schiff bases. But it cannot be confirmed as the
pound 1 was 16.731 A. The long distance showed
−
that the binding ability of the spherical anion (F )
FIGURE 9 Selected molecular orbital level of two compounds (1 and 2): (a) HOMO and (b) LUMO.
Heteroatom Chemistry DOI 10.1002/hc

148 Shang et al.
1
cis or trans isomer by H NMR, IR ,and elemental
analysis, since two isomers have the same element
tus. UV–vis spectroscopy titration was carried out
on a Shimadzu UV2550 spectrophotometer at 298
K. Fluorometric titration was performed on a Cary
Eclipse fluorescence spectrophotometer at 298 K.
The binding constant (Ks) was obtained by the non-
linear least-square calculation method for data fit-
ting. The kinds of bacteria used were colon bacil-
lus, S. aureus, S. albus, dysentery bacillus, and B.
subtilis. Nutrient broth was purchased from Aladdin
Reagent. An incubator (PYX-DHS), a sterilizer (LS-
C50L), and a superclean bench (YJ) were used. Qual-
itative analysis for screening of antibacterial activity
was carried out by the agar well-diffusion method
[25] with some modifications. The plates were kept
at 277 K for 2 h to allow the dispersal and then in-
cubated at 310 K for 24 h. Twenty milliliters of ster-
ilized nutrient agar was inoculated with 100 mL of
1
percentage and the difference of H NMR and IR
spectrum is very small. And we did not obtain the
crystal of compound 1. Therefore, we optimized the
geometries of two isomers using density functional
theory at the B3LYP/3-21G level with Gaussion03
program. Results indicated that the total energy
ET) of cis and trans isomers was –2574.3216724
and –2574.3216722 au, respectively. The energy
gap ꢀE(ELUMO – EHOMO) of cis and trans isomers
was 359.69 and 359.67 kJ·mol . ET and ꢀE of two
isomers were both very nearly same. Therefore,
compound 1 may be the mixture of two isomers.
However, the above conclusion did not affect the
anion-binding ability or antibacterial activity.
(
−1
7
bacterial suspension (10 CFU/mL) and then poured
onto a sterilized Petri plate. Two compounds were
resolved in the right amount of DMSO and were
CONCLUSIONS
−1
In conclusion, two new compounds bearing 2-
sulfydryl-thiodiazole were successfully designed and
synthesized. They showed strong binding ability
prepared to the solution (0.5 g·L ) by the addition
of H2O. The corresponding solvent (DMSO/H2O)
was blank experiment, and the effect of antibacte-
rial activity was determined by the dilution-plate
method.
–
for H2PO4 among studied anions and the anion-
binding ability of compound 2 containing an-
thracene was 1000 times stronger than that of com-
pound 1 containing nitrobenzene. In addition, two
compounds also illustrated wide antibacterial activ-
ity for Colon bacillus, S. aureus, S. albus, and Dysen-
tery bacillus. The important clue is provided for the
synthesis of novel compounds which have both prop-
erties of anion recognition and antibacterial activ-
ity. 2-Sulfydryl-thiodiazole derivatives can be used
as potential antibacterial and anion probes.
Two compounds (1 and 2) were synthesized ac-
cording to the route shown in Scheme 1.
Aminothiourea: Aminothiourea was synthesized
according to the literature method [26]. Yield: 83%.
◦
mp 179–180 C.
2-Sulfhydryl-5-amino-1, 3, 4-thiadiazole: It was
synthesized according to the literature method [26].
◦
Yield: 79%. mp 240–242 C.
Compound 1: 2-Sulfhydryl-5-amino-thiadiazole
(
(
2 mmol, 266 mg) was resolved in dry ethanol
20 mL). Three drops of ice acetic acid and 5-nitro-
1
,3-dialdehydebenzene (1 mmol, 179 mg) were
EXPERIMENTAL
added to the above solution, respectively. Then the
mixture was heated under refluxing in N2 for 12 h,
and yellow precipitate was separated by filtration.
The solid was recrystalled by ethanol, washed with
diethyl ether, and dried under vacuum. Yield: 87%.
mp >320 C. H NMR (400 MHz, DMSO-d6, 298 K)
δ 13.17 (s, 2H, SH), 10.64 (s, 2H, CH), 7.09 (s, 3H,
ph-H). Elemental analysis: Calcd for C12H7N7O2S4:
C, 35.20; H, 1.72; N, 23.94; Found: C, 35.48; H, 1.93;
Most of starting materials were obtained commer-
cially, and all reagents and solvents used were of
analytical grade. Hydrazine sulfate and all anions,
in the form of tetrabutylammonium salts (such
as (n-C4H9)4NF, (n-C4H9)4NCl, (n-C4H9)4NBr, (n-
C4H9)4NI, and (n-C4H9)4NAcO, (n-C4H9)4NH2PO4)
were purchased from Aladdin (Shanghai, People’s
Republic of China), stored in a desiccator un-
der vacuum containing self-indicating silica and
were used without any further purification. Tetra-
n-butylammonium salts were dried for 24 h in a
vacuum with P2O5 at 333 K before use. DMSO was
distilled in vacuo after dried with CaH2. C, H, and N
elemental analyses were carried out on a Vanio-EL
◦
1
−
N, 23.57. ESI-MS (m/z): 407.8 (M-H) .
Compound 2: It was synthesized according to
◦
1
the above process. Yield: 83%. mp >320 C. H NMR
(400 MHz, DMSO-d6, 298 K) δ 14.65 (s, 1H, SH), 9.82
(s, 1H, CH), 8.99–8.96 (d, 3H, ph-H), 8.22–8.21 (d,
2H, ph-H), 7.75–7.72 (t, 2H, ph-H), 7.65–7.61 (t, 2H,
ph-H). Elemental analysis: Calcd for C17H11N3S2: C,
63.53; H, 3.45; N, 13.07; Found: C, 63.27; H, 3.61; N,
1
elemental analyzer. H NMR spectra were recorded
on a Unity Plus-400 MHz spectrometer spectrome-
ter. ESI-MS was performed with a Mariner appara-
−
12.94. ESI-MS (m/z): 320.7 (M-H) .
Heteroatom Chemistry DOI 10.1002/hc

Synthesis, Bioactivity, and the Anion-Binding Property of 2-Sulfydryl-1,3,4-thiodiazole 149
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Heteroatom Chemistry DOI 10.1002/hc